给所有用户的 Artisan 命令通知给出了 BadMethodCallException

我如何创建一个 artisan 命令来向系统中的所有用户发送数据库通知，其中包含他们在系统中使用了多长时间的信息？

我的 SendEmails 命令如下所示：

    <?php

namespace App\Console\Commands;

use Illuminate\Console\Command;
use App\User;
use Illuminate\Support\Facades\Mail;
use App\Mail\UserEmails;
use Illuminate\Support\Facades\Notification;

class SendEmails extends Command
{
    /**
     * The name and signature of the console command.
     *
     * @var string
     */
    protected $signature = 'send:emails';

    /**
     * The console command description.
     *
     * @var string
     */
    protected $description = 'Send Email to allusers';

    /**
     * Create a new command instance.
     *
     * @return void
     */
    public function __construct()
    {
        parent::__construct();
    }

    /**
     * Execute the console command.
     *
     * @return mixed
     */
    public function handle()
    {
        $users = User::all();
        foreach($users as $user){
            $created_at = $user->created_at;
            Notification::send($user, new SendEmailsNotification($created_at));
        }
    }
}

然后我创建了通知表，进行了迁移，代码如下：

<?php

namespace App\Notifications;

use Illuminate\Bus\Queueable;
use Illuminate\Notifications\Notification;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Notifications\Messages\MailMessage;

class SendEmailsNotification extends Notification
{
    use Queueable;

    public $created_at;

    public function __construct($created_at)
    {
        $this->created_at = $created_at;
    }

    public function via($notifiable)
    {
        return ['database'];
    }

    public function toMail($notifiable)
    {
        return (new MailMessage)
                    ->line('The introduction to the notification.')
                    ->action('Notification Action', url('/'))
                    ->line('Thank you for using our application!');
    }

    public function toArray($notifiable)
    {
        return [
        ];
    }
}

用户.php：

<?php

namespace App;

use Illuminate\Notifications\Notifiable;
//use Illuminate\Contracts\Auth\MustVerifyEmail;
use Illuminate\Foundation\Auth\User as Authenticatable;

class User extends Authenticatable
{
    //use Notifiable;

    /**
     * The attributes that are mass assignable.
     *
     * @var array
     */
    protected $fillable = [
        'name', 'email', 'password', 'address', 'image'
    ];

    /**
     * The attributes that should be hidden for arrays.
     *
     * @var array
     */
    protected $hidden = [
        'password', 'remember_token',
    ];

    /**
     * The attributes that should be cast to native types.
     *
     * @var array
     */
    protected $casts = [
        //'email_verified_at' => 'datetime',
        'address' => 'array'
    ];

    protected $uploads = '/images/';

    public function getImageAttribute($image){
        return $this->uploads . $image;
    }

    public function contacts(){
        return $this->hasMany('App\Contact');
    }
}

当我运行工匠命令“php artisan send:emails”时，我在控制台中看到以下错误：

BadMethodCallException : 调用未定义的方法 App\User::routeNotificationFor()

如何向所有用户发送通知？